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AIS Antenna?
#1
Question 
Hi,

I now have the  RTL-SDR.COM USB SDR AIS receiver for my RPi3-Sensehat setup (see bragboard)

It came with both a mini and larger (maybe each arm nearly 1m long) version of a 'V' telescopic antenna.
I have read in another thread that the mini one is for FM radio, will the larger one work for AIS?

Or should I get another VHF antenna to mount on the pullpit?


Or can I use a splitter (for example this one) with my existing VHF antenna at the mast top?


Thanks

Leigh
  Reply
#2
looks here

http://vk2zoi.com/articles/half-wave-flower-pot/
Angel  Entschuldigung für mein Englisch. Es ist "google english"
PN bitte auf german.  Big Grin
  Reply
#3
I mounted a regular marine VHF antenna on the transom, which I use as my AIS antenna. It doesn't have as good range as if it were at the masthead, but my logic was that if I got de-masted I could use it as a backup VHF marine antenna.

Don't use a splitter - one good enough to prevent your marine VHF from overwhelming your AIS receiver would probably cost more than just a separate antenna and feedline.
  Reply
#4
i did test arround and depence of the use idid make some antennas myself and they work much better than antennas you can buy. The Antennas that come with and you have is in a realy good quality. A difference make the tram (arround 80-90$) Antenna i use. And i spoke with RTL-SDR.COM approx and we are looking both arround for some high quality antennas since half a year. I use some rtl-sdr sticks for drone or copter purposes. its in the plan of rtl-sdr to provide more things in the future. So a lots is by taste and very various.
  Reply
#5
What sort of range are you getting? There was a lot of discussion in other sailing forums about where to place AIS antennas. Apparently some offshore racing classes require that AIS antennas be at the masthead, giving range of up to 60 miles. I guess I could understand that for a racing yacht that is going 20 knots, but for an average sailor, I think a range of 10 miles or so is quite adequate, and perhaps even desired in busy areas.
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#6
(12-03-2017, 03:20 PM)abarrow Wrote: What sort of range are you getting? There was a lot of discussion in other sailing forums about where to place AIS antennas. Apparently some offshore racing classes require that AIS antennas be at the masthead, giving range of up to 60 miles. I guess I could understand that for a racing yacht that is going 20 knots, but for an average sailor, I think a range of 10 miles or so is quite adequate, and perhaps even desired in busy areas.

You can not compare my things with offshore racing. I am just a river traveller at the moment in Mass netherlands. Anyways i was mostly testing the 2 given Antennas with the Trust one and some you can find in the resources. And was for purpose to test with plane trafic. The antennas get for plane traffic betwhen 150 and 250 km I am not reading much in different forums mostly because of the english language that is used there. And you know here about my talents... Dodgy
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#7
Cheapest the best !
I built my AIS antanna from this video : https://www.youtube.com/watch?v=SdEglNHyHB4
Worked just fine from my terasse, I will attach it to the rear pulpit if de-masted or if the main antenna gets broken.
(My VHF outputs AIVDM sentences to the chart plotter).
Config : RPi 3, OP 1.0.0 alpha
Cordialement
Didier B





  Reply
#8
Thanks All,

I actually have an emergency VHF antenna that I had made myself over 10 years ago and had forgotten about!

I haven't tried the RPi system on the boat yet, only at home since the boat only went back in the water this week

When I get down to it I will try  my old DIY antenna (made with a bamboo stick and a two part simple wire, up and down) and then get to making some other ones as well for fun.

Thanks again

Leigh
  Reply
#9
(12-01-2017, 03:03 PM)Leigh Wrote: Hi,

I now have the  RTL-SDR.COM USB SDR AIS receiver for my RPi3-Sensehat setup (see bragboard)

It came with both a mini and larger (maybe each arm nearly 1m long) version of a 'V' telescopic antenna.
I have read in another thread that the mini one is for FM radio, will the larger one work for AIS?

Or should I get another VHF antenna to mount on the pullpit?


Or can I use a splitter (for example this one) with my existing VHF antenna at the mast top?


Thanks

Leigh
Yes you can use a splitter. There is nothing wrong with a modern well engineered splitter but as somebody said it will cost you money. 

This one from Vesper Marine is excellent https://www2.vespermarine.com/antenna-splitter-sp160

You really want you AIS antenna at the masthead for best performance.

You could put one another VHF antenna on the rail as a spare but I would still have the splitter. It is better to carry an emergency VHF antenna securely in a locker than have it mounted as if you loose your rig there is a fair chance that your spare VHF antenna is going to get swept overboard too. If you know how to make an emergency VHF antenna then there is only the need to carry some stiff wire. 

Typically you would make a 1/4 wavelength antenna. 

The formula is the speed of light (300x10^8 m/s) / frequency in MHz

3x10^8 / 162x10^6

=

300 / 162

=

1.8519m which is the wavelength of 162MHz so this has to be divided by four

1.8519 / 4 = 0.463m = the length of your antenna. 

Typical marine VHF antennas are longer than 1/4 wavelength and have loading coils at the bottom to give better performance but a 1/4 wavelength like this on the stern will work fine in an emergency.
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#10
(12-09-2017, 05:53 PM)Littlechay Wrote:
(12-01-2017, 03:03 PM)Leigh Wrote: Hi,

I now have the  RTL-SDR.COM USB SDR AIS receiver for my RPi3-Sensehat setup (see bragboard)

It came with both a mini and larger (maybe each arm nearly 1m long) version of a 'V' telescopic antenna.
I have read in another thread that the mini one is for FM radio, will the larger one work for AIS?

Or should I get another VHF antenna to mount on the pullpit?


Or can I use a splitter (for example this one) with my existing VHF antenna at the mast top?


Thanks

Leigh
Yes you can use a splitter. There is nothing wrong with a modern well engineered splitter but as somebody said it will cost you money. 

This one from Vesper Marine is excellent https://www2.vespermarine.com/antenna-splitter-sp160

You really want you AIS antenna at the masthead for best performance.

You could put one another VHF antenna on the rail as a spare but I would still have the splitter. It is better to carry an emergency VHF antenna securely in a locker than have it mounted as if you loose your rig there is a fair chance that your spare VHF antenna is going to get swept overboard too. If you know how to make an emergency VHF antenna then there is only the need to carry some stiff wire. 

Typically you would make a 1/4 wavelength antenna. 

The formula is the speed of light (300x10^8 m/s) / frequency in MHz

3x10^8 / 162x10^6

=

300 / 162

=

1.8519m which is the wavelength of 162MHz so this has to be divided by four

1.8519 / 4 = 0.463m = the length of your antenna. 

Typical marine VHF antennas are longer than 1/4 wavelength and have loading coils at the bottom to give better performance but a 1/4 wavelength like this on the stern will work fine in an emergency.

Thanks Chris
  Reply


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